Seismic exploration typically involves use of a seismic energy source for generating an input of seismic energy into the earth formations and detection of the seismic energy reflections from subsurface strata at one or more spaced geophone stations. If the energy source is used to generate a single impulse of energy, such as a Ricker Wavelet, then the exclusion of subsequent cycles of energy input from the energy source is desirable. However, mechanical seismic energy sources which utilize dropping a weight are difficult to control and are slow in operation. Hydraulic systems which accelerate a weight as an impulse source are more efficient, but, in the past, have not effectively eliminated additional shock waves from the energy source following an initial shock or seismic impulse.
Heretofore, a hydraulically accelerated weight system has been developed as an inexpensive source of a seismic impulse energy. In this system, a weight or mass is accelerated by a hydraulic pressure source to contact the earths surface with sufficient force to obtain seismic reflections from subsurface strata in the shallow to medium depths. The system, aside from being simple and inexpensive, can operate repeatedly several thousand times a day without breakdowns or surface damage. The system can be mounted on a movable vehicle which is capable of getting in and out of places that other sources would have difficulty in operating.
The present invention is concerned with improvements for such a hydraulic accelerated weight system for creating a controlled seismic impulse and eliminating an subsequent "after shock" of an accelerated weight after an initial impact with the surface of the earth.